This invention relates to a method and device for improving the efficiency of electricity generators.
In the past, electricity generators have suffered from some loss of efficiency as a result of magnetic flux distortion created by the generated current in the generator.
In a typical generator, there is a magnetic flux path passing through a stator and through a rotor. As a primary magnetic flux varies in the flux path, an electric voltage and, when the circuit is closed, an electric current is induced in a conductor that surrounds, or is coiled about, a portion of the flux path. This conductor is usually referred to as an armature coil. As the induced current varies in the armature coil, a second magnetic flux is induced in the magnetic flux path by the induced current. The second magnetic flux will be referred to as the "generated flux" or as the "secondary flux". The generated flux distors the primary magnetic flux when the induced current in the armature coil has an ohmic component.
In the event current is absent in the armature coil, or when the armature coil is short circuited, or the load across the armature coil is purely reactive, the primary magnetic flux, at a pole face between the stator and rotor, is symmetrical about the centre of the face. Thus, the magnetic attraction between the rotor pole and the stator pole is symmetrical about the centre of the pole face. Thus, the energy stored by moving the rotor pole face towards and into alignment with the stator pole face is the same as the energy expended in moving the rotor pole face out of alignment and away from the stator pole face. Therefore, other than frictional, windage and iron losses, the energy required to rotate the rotor is zero when only the primary magnetic flux is in the flux path or when the magnetic flux pattern or shape is made symmetrical across the face of the pole.
However, when the primary magnetic flux is distorted by the generated flux induced in the armature coil, the magnetic flux is no longer symmetrical across the pole face between the stator and rotor. Thus, the energy stored in moving the rotor pole face towards and into alignment with a stator pole face is no longer equal to the energy required to move the rotor pole face out of alignment and away from the stator pole face. Thus, additional energy is required to rotate the rotor when current having an ohmic component is induced in the armature coil. The power required to rotate the rotor when current is induced in the armature coil, as compared to the power input when there is no current induced in the armature coil, will be referred to as the "distorted power input requirement".